The present invention relates to the field of compression ignition engines, and more particularly to the field of electronic control of the power output of compression ignition engines.
Electronically controlled compression ignition engines are known in the art, but vary in the degree of sophistication in the control schemes they employ. In general, the electronic controllers associated with such engines are connected with fuel injection devices that inject a predetermined amount of fuel at a predetermined time into each of the cylinders of the engine based on a corresponding fuel injection signal produced by the controller. The fuel injection signals therefore determine the amount of fuel injected into the cylinders and the power output of the engine.
Depending on the specific application, the electronic controller may be connected with a variety of different operator inputs and other sensors including a throttle sensor input, cruise control settings, and various engine and transmission sensor inputs, among others. The electronic controller receives inputs from these sensors and determines the fuel injection signal which may be a function of many factors, including the overall amount of fuel to be injected, and the shape, number, duration and timing of individual injections for a particular engine cylinder. The characteristics of the fuel injection signal will determine the overall power output of the engine. In some engine applications there are fuel delivery limits that are stored in memory, or otherwise associated with the electronic controller. In particular applications where the operator, cruise control or other aspect of the electronic controller might otherwise request a fuel injection signal that would cause the engine to produce a power output greater than the rated horsepower output of the engine, the controller will limit the amount of fuel delivered as a function of the fuel delivery limit curve, which therefore limits the power output of the engine.
Those skilled in the art will recognize that engines used in work equipment applications are typically required to provide power to at least two different kinds of loads: work loads; and parasitic loads. In general, work loads are devices or systems that produce a net work output from the work equipment and generally include a transmission which demands power from the engine to propel the wheels, tracks, or other ground engaging propulsion mechanism, and a hydraulic system which demands power from the engine to move a bucket, for example, to dig and move dirt or earth. Parasitic loads, in contrast, are typically characterized as those loads that demand power output from the engine, but do not produce actual work output from the work equipment. Devices that may fall in this category include an engine cooling fan, a compressor for an air conditioning system, an alternator and other devices. For example, the engine cooling fan requires engine power to draw air through the radiator to cool the engine. The compressor requires engine power to run the air conditioning system and the alternator requires engine power to generate electrical power to recharge batteries and run electrical accessories. These parasitic loads reduce the amount of power that is available to the work loads.
Electronically controlled compression ignition engines that are known in the art do not vary the output power of the engine based on parasitic loads. Because the parasitic loads decrease the power available for work loads, the work load power of such engines will vary depending on the overall engine power output and the amount of power required by the parasitic loads. Because the parasitic load will vary depending on various conditions, work equipment operators are often unable to determine the amount of work power that will be available. For example, when the work equipment is operated in the morning and the temperature is relatively cool, the cooling fan may require little or no power to maintain a desired engine operating temperature. As the ambient temperature increases during the day, more power may be required by the cooling fan to maintain the desired engine temperature, and the operator may notice an undesirable decrease in the amount of engine power available to do work.
It would be preferable to have a system that generated a relatively constant workload power output. These and other aspects and advantages of present invention will become apparent upon reading the detailed description in connection with the drawings and appended claims.
In one aspect of the present invention a system for controlling fuel delivery to a compression ignition engine is disclosed. Prefereably the engine controllably powers at least a transmission or a work implement system, and one other device. The system includes an electronic control module connected with the other device and the transmission or work implement system. A fuel injection device is also connected with the electronic control module. The electonic control permits the engine to produce a first power output when the other device does not demand power, and a second power output when the other device demands power.